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This invention relates in general to techniques for tracking mobile items and, more particularly, to a method and apparatus for tracking mobile items using radio frequency tags.
Various techniques have been developed for tracking mobile devices. According to one existing technique, a device known as a radio frequency identification tag is mounted on the device, and communicates by means of radio frequency signals with a central receiver which is commonly known as a reader. While existing arrangements of this type have been generally adequate for their intended purposes, they have not been satisfactory in all respects.
For example, a mobile device which is being tracked may be supported on some other type of mobile device, such as a forklift, making it difficult for existing tracking systems to determine whether or not a given mobile device is currently supported on a different mobile device. A further consideration is that it may be difficult with existing technology to determine whether two mobile devices, such as a tractor and trailer, are currently coupled to each other, or are simply in the same general vicinity. Also, where two or more mobile devices such as containers are supported on respective different mobile devices such as trailers that are all near each other, it can be difficult with existing technology to determine which mobile device is supporting which other mobile device.
From the foregoing, it may be appreciated that a need has arisen for a method and apparatus for effecting more accurate tracking of mobile items using radio frequency technology. According to a first form of the present invention, a method and apparatus are provided to address this need and involve: transmitting signpost signals from a signpost, each signpost signal having a signpost code; receiving the signpost signals in a receiver section of circuitry of a tag which is physically separate from the signpost; transmitting from a transmitter section of the circuitry of the tag wireless beacon signals which each include a beacon code associated with the tag, the transmitting step including the step of causing the transmitter section to be responsive to receipt by the receiver section of a respective signpost signal for including in at least one beacon signal the signpost code from the received signpost signal; receiving the beacon signals in a reader which is physically separate from the signpost and the tag; removably supporting on a mobile device an item having the tag disposed thereon; stationarily supporting the signpost near a path of travel of the mobile device in a manner so that the tag passes through a transmission range of the signpost signals from the signpost as the mobile device travels past the signpost with the item thereon; supporting near the path of travel of the mobile device a sensor which is operatively coupled to the signpost; detecting proximity to the sensor of one of the item and the mobile device; and responding to detection by the sensor of the proximity of the one of the item and the mobile device for effecting a change in the signpost code of the signpost.
A different form of the present invention involves: transmitting signpost signals from a signpost, each signpost signal including a signpost code; receiving the signpost signals in a receiver section of circuitry of a tag which is physically separate from the signpost; transmitting from a transmitter section of the circuitry of the tag wireless beacon signals which each include a beacon code associated with the tag, the transmitting step including the step of causing the transmitter section to be responsive to receipt by the receiver section of a respective signpost signal for including in at least one beacon signal the signpost code from the received signpost signal; receiving the beacon signals in a reader which is physically separate from the signpost and the tag; supporting the signpost on a mobile device; and removably supporting on the mobile device an item having the tag disposed thereon at a location so that the tag is within a transmission range of the signpost signals from the signpost while the item is removably supported on the mobile device.
Yet another form of the present invention involves: transmitting signpost signals from a signpost, the signpost signals each including a signpost code; receiving the signpost signals in a receiver section of the circuitry of a tag which is physically separate from the signpost; transmitting from a transmitter section of the circuitry of the tag wireless beacon signals which each include a beacon code associated with the tag, the transmitting step including the step of causing the transmitter section to be responsive to receipt by the receiver section of a respective signpost signal for including in at least one beacon signal the signpost code from the received signpost signal; receiving the beacon signals in a reader which is physically separate from the signpost and the tag; releasably coupling first and second mobile devices to each other; and supporting the signpost on one of the mobile devices and the tag on the other thereof, in a manner so that the tag is within a transmission range of the signpost signals from the signpost while the mobile devices are releasably coupled.